1. Field of the Invention
The present invention relates to a substrate heat treatment apparatus irradiating a substrate such as a semiconductor wafer, a glass substrate for a photomask, a glass substrate for a liquid crystal display or a substrate for an optical disk (hereinafter simply referred to as xe2x80x9csubstratexe2x80x9d) for performing heat treatment.
2. Description of the Background Art
As refinement of a semiconductor device or the like is strictly required, a rapid heat treatment process referred to as an RTP (rapid thermal process) is watched with interest as one of heating steps for a substrate.
FIG. 17 is a longitudinal sectional view of a conventional RTP apparatus. In the RTP, the following treatment is performed with this apparatus: Lamps 91a, 91b and 91c are employed as heating sources, and treatment gas (e.g., nitrogen gas or oxygen gas) responsive to the treatment process is supplied into a treatment chamber 90 from a gas inlet port 90a for keeping the treatment chamber 90 in such a gas atmosphere, heating a substrate W to a desired temperature (up to about 1200xc2x0 C.) in order of seconds, holding the substrate W at the temperature for a desired time (several 10 seconds) and thereafter turning off the lamps 91a to 91c and rapidly cooling the substrate W.
This apparatus, capable of preventing impurities from re-diffusion caused by heat in junction layers of transistors formed on the substrate W and forming an insulator film such as a thin oxide film, can perform treatment which has been hard to implement by conventional long-time high-temperature heat treatment with an electric furnace.
In the conventional apparatus, the cylindrical lamps 91a to 91c are embedded in a reflector 93 having a cylindrical reflecting surface 95 as shown in FIG. 17, in order to apply emitted light to the substrate W with a certain degree of directivity.
In general, however, light emitted from filaments 94 is mainly applied in a direction (hereinafter referred to as xe2x80x9cside surface directionxe2x80x9d) perpendicular to the longitudinal direction of the filaments 94, i.e., in the direction (along an X-Y plane) of the cylindrical reflecting surface 95 of the reflector 93 in the apparatus shown in FIG. 17. In other words, the light is intensely applied toward the side surface direction and extremely weakly applied in the longitudinal direction (Z-axis direction) of the filaments 94. Therefore, most of the light emitted from the filaments 94 is multiple-reflected in the cylindrical reflecting surface 95 to thereafter outgo from the lower end of the cylindrical reflecting surface 95. Also in this case, the light mainly outgoes in the side surface direction, and the optical path toward the substrate W may be elongated to attenuate the light, leading to inferior heating efficiency for the substrate W.
Most of the light in the aforementioned side surface direction reaches the cylindrical reflecting surface 95, to be partially absorbed by the cylindrical reflecting surface 95. It follows that most of the light reflected by the cylindrical reflecting surface 95 returns to the lamps 91a, 91b and 91c, and hence the cylindrical reflecting surface 95 and the lamps 91a to 91c reserve heat to be deflected due to high temperatures or inhibit the halogen cycle of halogen gas in glass tubes 96 provided in the lamps 91a to 91c, leading to reduction of the lives of the lamps 91a to 91c. 
In the RTP, temperature distribution in the substrate surface (X-Y plane) of the substrate W is desirably uniform. In order to improve temperature uniformity of the substrate W, therefore, radiation thermometers 92a, 92b and 92c are provided in correspondence to a center area CA, a middle area MA and an edge area EA respectively, for example, in the substrate surface for measuring the temperatures of the aforementioned areas CA, MA and EA respectively while the plurality of lamps 91a, 91b and 91c are provided in correspondence to the areas CA, MA and EA respectively for feedback-controlling power supplied to the lamps 91a to 91c for the areas CA, MA and EA so that the substrate temperatures on the respective areas CA, MA and EA match with each other.
However, the temperatures of intermediate portions between the center area CA and the middle area MA and between the middle area MA and the edge area EA, for example, are not measured, and these intermediate portions located between the areas CA, MA and EA cannot be selectively temperature-controlled. Therefore, the temperature of the substrate W is ununiform on these intermediate portions. Temperature ununiformity in these intermediate portions is further described.
FIG. 18 is a plan view showing lamp arrangement in the conventional RTP apparatus. This RTP apparatus comprises a lamp group 99 formed by 19 lamp units 98. Each lamp unit 98 is formed by a lamp 91 and a cylindrical reflecting surface 95. As shown in FIG. 18, the lamp group 99 is in honeycomb arrangement having six lamp units 98 adjacently provided around a single lamp unit 98. The lamp group 99 is arranged to cover the overall surface of a substrate W with the 19 lamps 91. The diameter of the substrate W is 200 mm.
In order to heat-treat the substrate W with the lamp group 99, each lamp 91 is supplied with power to emit light. The light outgoing from each lamp 91 reaches the substrate W directly or after reflected by the cylindrical reflecting surface 95, to heat the substrate W. At this time, the lamp group 99 is divided into three areas consisting of a center area formed by the centermost lamp 91, an edge area formed by 12 outermost lamps 91 and a middle area formed by six intermediately located lamps 91 for varying power supply patterns with the areas while rotating the substrate W, thereby ensuring inplane temperature uniformity of the substrate W.
However, the conventional heat treatment apparatus cannot ensure sufficient inplane temperature uniformity despite the aforementioned power supply control for each area and rotation of the substrate W. The reason for this is now described.
FIG. 19 illustrates illuminance distribution on the substrate W with a single lamp 91. Referring to FIG. 19, the left-end position (position of a distance zero) is a position immediately under the lamp 91 in the vertical direction on the substrate W. Symbol RP denotes the radius of the lamp 91.
While high illuminance is obtained on the position immediately under the lamp 91, illuminance on the substrate W tends to gradually lower as the distance from this position is increased. In other words, the light emitted from the lamp 91 has downward directivity due to the cylindrical reflecting surface 95 and hence substantially uniform high illuminance is obtained immediately under the lamp 91 (within the range of the diameter of the lamp 91), while illuminance of the light emitted from the lamp 91 lowers as the horizontal distance (direction parallel to the surface of the substrate W) from the lamp 91 is increased.
On the other hand, the 19 lamps 91 forming the lamp group 99 is arranged in the form of a honeycomb as described above, and it can be said that the 19 lamps 91 are arranged on concentric circles in another point of view. Therefore, the conventional heat treatment apparatus exhibits illuminance distribution shown in FIG. 20 also when rotating the substrate W.
FIG. 20 illustrates radial illuminance distribution on the substrate W in the conventional heat treatment apparatus. As shown in FIG. 20, a certain degree of illuminance is attained in positions on the substrate W under the aforementioned center area, the middle area and the edge area respectively, while illuminance lowers in positions under the intermediate portions between the areas. Each lamp 91 applies a sufficient quantity of light under the center area, the middle area and the edge area to increase illuminance due to the illuminance distribution of the light emitted from each lamp 91 shown in FIG. 19, while the quantity of light emitted from each lamp 91 is reduced to lower illuminance in the portions under the clearances between the areas. The substrate W is rotated when irradiated with light, and hence illuminance is substantially uniform in the same area to exhibit the illuminance distribution shown in FIG. 20 as to an arbitrary radial direction of the substrate W.
When the radial illuminance distribution on the substrate W is ununiform as shown in FIG. 20, in-plane temperature uniformity in the substrate W is disadvantageously damaged as a result.
The present invention is directed to a heat treatment apparatus irradiating a substrate with light for performing heat treatment.
According to the present invention, a heat treatment apparatus rotating a substrate and irradiating the substrate with light for performing heat treatment comprises a lamp group having a plurality of lamps, each irradiating the substrate with light, arranged to have n-fold rotation symmetry (n: natural number of at least 2) about a prescribed symmetry axis and a rotation driving part rotating the substrate about a rotation axis substantially parallel to the symmetry axis, while the symmetry axis and the rotation axis are displaced along a direction substantially parallel to the surface of revolution of the substrate.
Peaks and bottoms of illuminance distribution on the substrate resulting from regularity of arrangement of the lamp group are relaxed due to rotation of the substrate, whereby uniformity of radial illuminance distribution on the substrate is improved so that temperature uniformity of the substrate can be ensured in heat treatment.
According to a preferred embodiment of the present invention, the symmetry axis and the rotation axis are displaced by at least ⅕ and not more than xc2xd the interval of arrangement of the plurality of lamps.
Uniformity of radial illuminance distribution on the substrate is so remarkably improved that temperature uniformity of the substrate can be ensured in heat treatment.
According to another embodiment of the present invention, a heat treatment apparatus irradiating a substrate with light for performing heat treatment comprises a holding part holding the substrate and an irradiation part having a light source and a reflecting surface reflecting light emitted from the light source for irradiating the substrate held by the holding part with light, while the reflecting surface includes a cylindrical first surface having a symmetry axis in a direction substantially perpendicular to the substrate and a second surface connected on an end of the first surface closer to the substrate and spread on a side closer to the substrate.
Light reflected sideward by the end closer to the substrate after multiple-reflected in the cylinder of the first surface is also reflected by the second surface toward the substrate to be collected, whereby directivity of irradiation toward the substrate is excellent and heating efficiency for the substrate is improved while the light can be concentrated in the vicinity of a portion on the substrate corresponding to the light source, whereby temperature control on this portion is simplified. Further, a cylindrical portion is relatively small as compared with the case of forming the reflecting surface only by a cylindrical reflecting surface, whereby quantities of heat reserved in the light source and the reflecting surface are small and the lives thereof can be increased.
According to still another embodiment of the present invention, a heat treatment apparatus irradiating a substrate with light for performing heat treatment comprises a holding part holding the substrate, a light source opposed to the substrate held by the holding part for irradiating the substrate with light and a light source position control part capable of controlling the distance between the light source and the substrate held by the holding part.
The quantity of light applied to the periphery of a region of the substrate corresponding to the light source can be adjusted by controlling the distance between the light source and the substrate, whereby temperature uniformity of the substrate can be improved for performing high-quality heat treatment.
Accordingly, an object of the present invention is to provide a heat treatment apparatus capable of ensuring temperature uniformity of a substrate in heat treatment.
Another object of the present invention is to provide a heat treatment apparatus having excellent heating efficiency with a long life of a light source or the like.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.